Cast-steel ladle



June 28 1927 E. G. sWlGERT CAST STEEL LADLE Filed All-Y.. 51. 1925 Patented June 28, 19,27.

UNITED*A STATES ERNEST e. sWIGRRr, or PORTLAND, OREGON.

CAST-STEEL LADLE.

.Application led August 31, 1925. Serial No. 53,525.

My invention relates to ladles and other containers by which molten met-al is moved about in smelters, and'my invention relates especially to ladles used in copper smelteis, which because of their large sizeand thick walls are subjected to unequal expansion in their inner and outer surfaces when heated by the molten metal within the ladle. In other Words't-he molten metal poured into the ladle heats first the interior surface thereof and the heat conducted through the 'thick walls to the outer surface of the ladle ,is not suliicient 'to raise the latter surface to the same temperature as thatof the inner surface; in consequence such unequal heating causes unequal expansion of' thel inner andouter portions ofthe side walls and the bottom of the ladle. The inner portion of the ladle wall is restrained in its expansion by the cooler outer surface of the wall and -is subjected to compression, `but since the metal in this portion of the wall and bottom becomes partially fluid it pushes inward forming protuberances like minutecorruga tions or ridges. Then whenl the ladle is emptied, the, interior of the wall has to cool through a greater range of temperature than the outer portion and thus undergoes greater shinkage. But the interior shrinkage is again restrained by the lesserl shrinkage of the outer ortion and the strain .thus produced in t e. metal causes cracking or rcrazing of the ladle wall. pronounced in the bottom of the ladle than 1n the sides, and the cracks in the bottom frequently extend entirely through the ladle, resulting in fracture.

Increasing the thickness of the wall of the` ladle in order to prevent the cracks extending entirely through the wall is unsatisfactory for it increases difference in both exi pansion .and shrinkage of the inner and outer wall'surfaces, and resultsin the pro-- motion of crazing and the formation of wider cracks. If, on the other hand, the wall is made thinner, the strength of the ladle becomes insufficient for practical use.

The crazing. cracking, and fracturing of ladles as described above is not ordinarily serious in the case of cast iron ladles, because the rate ofcooling of cast iron and the eX- tent of shrinkage do not produce internal strains of such magnitude as to cause serious fracture of the metal. But in the cast steel ladles, the rapid cooling and relatively -greater shrinkage acts upon the structure of This effect is more" the metal to such an extent as to fracture the bottom of the ladle and render it practically Worthless within a short time. Itis therefore common practice at the present time to make ladles of cast iron rather than cast steel. For ladles of large size, however, such as those used in copper smelters, I prefer to make the ladles of cast steel, for the reason that cast iron is so brittle and easily shattered when struck by a sharp blow; and of course a ladle full of molten metal andl subject to momentary breakage is a source of continual danger to the workmen.

The ,object of my invention is to produce a cast steel ladle, and the like, which is adapted to resist said dangerous crazing and cracking tendency, by neutralizing the causes of such effects.

I attained my object by the discovery that said crazing and' cracking tendency .may be the ladle is adapted to be bent or iexed inward and outward, and thus to accommodate and neutralize the strains in the metal due to said unequal expansion and shrinkage, caused by the unequal temperatures induced in the interior and exterior surfaces of the ladle by the heat of the material carried therein. In this way the fracturing of the ladleby said unequal expansion and vsubstantially eliminated by a change in the vshrinkage is minimized toa negligible degree. vIn fact,vin m 4practice I found that said fracturing ten ency was eliminated.

The details of construction of a preferred embodiment of my invention are hereinafter described with reference to the accompanying1 drawings, in which:

ig. 1 is a plan view of a ladle embodying my invention; and f' Fig. 2 -is a. ylongitudinal section therethrough taken on the line 2 2 of Fig. 1.

My improved ladle a is an integral structure comprising a body of convenlent form, having walls and a bottom of substantial and uniform thickness. The ladle is provided with trunnions b, a pouring spout c, spaced leg portions d and a tipping eye e, which serve their usual purposes.

'ilo

The intense heat from the molten metal ladle, and the successive. heating and cooling Walls of the ladle to become correspondingly hea-ted. `When the ladle is filled with molten metal the 'heat from the latter is of course communica-ted to a greater degree to theJ interior surface of the ladle than its exterior surface, difference in the heating of its inyner and outer surfaces varying according to the' fractures usually occur is in the bottomI a of the ladle. The heat applied to the inner surface tends either to deform the curvature 'of the bottom or to elongate it relatively to the outer surface and the latter being relatively cooler tends to resist said elongation. The inner surfaces being heated to a relatively high degree thus become partially fluid and thus the internal stresses Within the f Wall causes Welts or ridges to be formed upon the inner surface of thebottom of the ladle. lieved upon cooling, the contraction of the metal does not cause said protuberances tov recede, but instead causes cracks to form between said ridges or Welts. Said cracks eX- tend pa'rtlally through the bottom of the When said stresses are re-y action. to which the ladle is subjected by conveying and discharging batches of molten metal, soon extends these cracks completely through the ladle so as to render the same Worthless. To prevent such result I form the bottom a of the ladle with a concavo-convex central portion a2. As shown in Fig. 2, the bottom Aof the ladle is not increased in thickness and isl substantially of `uniform, thickness throughout and thus the inner surface of said concaveconvex central portion is curved upon an are having a greater radius than the concentrically curved outer portion of the bottom. The result of so `forming the bottom of the ladle is, the bottom is adapted to be bent or flexed inward and outward more or less in accommodating said unequal expansion of its inner and outer surfaces, and in that Way the detrimental strains caused. in the metal are neutralized and substantially eliminated, thus avoiding the danger -of fracturing the ladle, and not only prolonging the life of the latter but also protecting the Workmen using it. v

I claim:

A ladle adapted for carrying Imolten metal inducing interior heating, the bottom of the ladle belng formed of substantially uniform thickness, and with an incurved area Whereby the linear dimensions of the bottom between diametrically opposed points in the side walls of the ladle are increased to permit unequal expansion and shrinkage of the bottomv and neutralize the strains tending. to cause crazing and cracking of the bottom.

ERNEST Gr. SWIGERT. 

